JP2021035195A - Power converter - Google Patents

Abstract

To provide a power converter that is able to securely correct a zero point of an electrical current sensor, compared to a conventional power converter.SOLUTION: A power converter disclosed in the present description comprises a boosting circuit, a power conversion circuit, an electrical current sensor, and a control unit. The boosting circuit has a first switching element that boosts a voltage of a power source. The power conversion circuit has a second switching element that converts output of the boosting circuit into drive power for a travel motor. The electric sensor measures an electrical current flowing between the power source and the travel motor. The control unit controls the first switching element and the second switching element. The control unit turns off both the first switching element and the second switching element and, based on the measurement values of the electrical current sensor at the time, corrects a zero point of the electrical current sensor. This power converter acquires a measurement value for the zero-point correction after bringing about a state in which an electrical current flowing through the power converter is securely made to be zero by turning off the switching element for boosting and the switching element for power conversion.SELECTED DRAWING: Figure 4

Description

The techniques disclosed herein relate to power converters.

For example, an electric vehicle is equipped with a power converter that converts the output of a power source into the driving force of a traveling motor. This power converter includes a booster circuit including a switching element that boosts the output voltage of the power supply, and a power conversion circuit including a switching element that converts the boosted power into the driving force of a traveling motor. There is. Such a power converter is provided with a current sensor that detects the flowing current, and the controller of the power converter controls the switching element by the current value detected by the current sensor.

If an error occurs in the current sensor that detects the current flowing through the power converter, the output of the power converter cannot be controlled accurately. If an error occurs in the current sensor, the output of the current sensor may indicate a value other than zero even though no current is actually flowing. This phenomenon is known as the deviation of the zero point (origin).

For example, Patent Document 1 discloses a technique for correcting a deviation of a zero point. Patent Document 1 includes a voltage conversion circuit including a series connection of two switching elements, and a power conversion circuit connected to the voltage conversion circuit. The switching element on the low potential side (lower switching element) connected in series is involved in the boosting operation of boosting the voltage of the power supply and supplying it to the inverter. The switching element on the high potential side (upper switching element) is involved in the step-down operation of stepping down the power generated by the motor (regenerative power) and supplying it to the power source. The state in which a current flows from the power supply to the motor is called power running. In the power converter of Patent Document 1, both the upper switching element and the lower switching element are kept off, and the measured value of the current sensor is acquired at the timing when power running and regeneration are switched. The direction of current flow reverses at the timing of switching between power running and regeneration. At the timing when the direction of current flow is reversed, no current flows through the power converter. The power converter of Patent Document 1 acquires the measured value at that timing as an offset of the zero point.

Japanese Unexamined Patent Publication No. 2013-110932

The technique of Patent Document 1 corrects the deviation of the zero point based on the measured value of the current sensor at the timing when the current stops flowing when switching from power running to regeneration. However, in the technique of Patent Document 1, if the acquisition timing of the measured value of the current sensor deviates even slightly, the accuracy of correcting the deviation of the zero point decreases. The present specification provides a power converter capable of correcting the zero point of a current sensor more accurately than before.

The power converter disclosed in the present specification includes a booster circuit, a power conversion circuit, a current sensor, and a controller. The booster circuit has a first switching element that boosts the voltage of the power supply. The power conversion circuit has a second switching element that converts the output of the booster circuit into the drive power of the traveling motor. The current sensor measures the current flowing between the power supply and the traction motor. The controller controls the first switching element and the second switching element based on the measured value of the current sensor. The controller turns off both the first switching element and the second switching element, and corrects the zero point of the current sensor based on the measured value of the current sensor at that time. That is, the power converter disclosed in the present specification creates a state in which both the first switching element for boosting and the second switching element for power conversion are turned off so that the current flowing through the power converter is surely zero. Obtain the measured value for zero point correction from. Therefore, the zero point can be corrected accurately.

The booster circuit may include a reactor connected between an input terminal connected to a power supply and a first switching element. On the other hand, the Hall element method is often adopted for the current sensor to obtain the measured value of the current by utilizing the Hall effect from the magnetic flux generated due to the current to be measured. In such a case, if even a small amount of current is flowing through the reactor, the measured value of the current sensor will further include an error due to the magnetic field generated by the reactor. The techniques disclosed herein are unaffected by the magnetic field of the reactor because they create a state in which the current actually flowing through the reactor is zero.

Details of the techniques disclosed herein and further improvements will be described in the "Modes for Carrying Out the Invention" below.

It is a circuit diagram of the electric vehicle equipped with the power converter of an embodiment. It is a side view of the power converter of an Example. It is sectional drawing of the power converter cut by the line III-III of FIG. It is a processing flow diagram which a controller included in the power converter of an Example executes.

The power converter of the embodiment will be described with reference to the drawings. The circuit included in the power converter 1 of the embodiment will be described with reference to FIG. The power converter 1 is mounted on the electric vehicle 100. As shown in FIG. 1, the power converter 1 is connected to a battery 2 which is a power source of the electric vehicle 100 and a motor 8 which drives the wheels of the electric vehicle 100. The power converter 1 converts the DC voltage of the battery 2 into the driving power of the motor 8. The motor 8 is a three-phase AC motor. The power converter 1 boosts the DC voltage of the battery 2 and converts the boosted power into three-phase AC.

As shown in FIG. 1, the power converter 1 includes a converter circuit 4 as a booster circuit. Further, the power converter 1 includes an inverter circuit 6 as a power conversion circuit. Further, the power converter 1 includes a converter circuit 4 and a controller 10 for controlling the inverter circuit 6. The converter circuit 4 is a chopper-type bidirectional DC-DC converter circuit that boosts the voltage of the battery 2 and supplies it to the inverter circuit 6. The converter circuit 4 can also step down the regenerated power generated by the motor 8 (after the inverter circuit 6 converts it to DC power) to the voltage of the battery 2.

As shown in FIG. 1, a filter capacitor 12 is connected between the battery 2 and the converter circuit 4. A smoothing capacitor 14 is connected between the converter circuit 4 and the inverter circuit 6.

The converter circuit 4 includes a semiconductor module 30, a reactor 20, and a current sensor 22. The semiconductor module 30 includes a series connection of a plurality of voltage switching elements 32 and 34 for boosting the voltage of the battery 2. Diodes are connected in antiparallel to each of the voltage switching elements 32 and 34 of the semiconductor module 30. The reactor 20 is connected between an input terminal connected to a battery 2 which is a power source and a semiconductor module 30 including voltage switching elements 32 and 34. The current sensor 22 is connected between the reactor 20 and the semiconductor module 30 and measures the current flowing through the reactor 20. The current sensor 22 measures the current flowing through the converter circuit 4. The dashed arrow in the figure shows the signal flow. The measured value of the current sensor 22 is sent to the controller 10. The controller 10 controls the voltage switching elements 32 and 34 based on the measured value of the current sensor 22.

As described above, the converter circuit 4 is a bidirectional DC-DC converter. Since the function of the converter circuit 4 is well known, the description thereof will be omitted.

The inverter circuit 6 will be described. The inverter circuit 6 converts the DC power boosted by the converter circuit 4 into AC power that drives the motor 8. As shown in FIG. 1, the inverter circuit 6 has a circuit structure in which semiconductor modules 40, 50, and 60 are connected in parallel. The semiconductor module 40 includes a series connection of two conversion switching elements 42 and 44 that convert the output of the booster circuit (converter circuit 4) into the drive power of the traveling motor. Diodes are connected in antiparallel to each of the conversion switching elements 42 and 44 of the semiconductor module 40. The semiconductor modules 50 and 60 also include a series connection of two conversion switching elements (a series connection of the conversion switching elements 52 and 54 and a series connection of the conversion switching elements 62 and 64). Since it has the same structure, the description thereof will be omitted. Further, as shown in FIG. 1, the inverter circuit 6 is connected to the motor 8 via the power cable 18. The output of the inverter circuit 6 is sent to the motor 8 via the power cable 18. Further, a current sensor 16 is connected between the inverter circuit 6 and the motor 8. The current sensor 16 measures each of the three-phase alternating currents sent by the inverter circuit 6 to the motor 8. The current sensor 16 measures the current flowing between the battery 2 and the motor 8. The measured value of the current sensor 16 is sent to the controller 10. Based on the measured value of the current sensor 16, the controller 10 controls a plurality of conversion switching elements 42, 44, 52, 54, 62, 64 included in the inverter circuit 6. In the following, a plurality of voltage switching elements 32 and 34 included in the converter circuit 4 may be collectively referred to as a voltage switching element group. Further, a plurality of conversion switching elements 42, 44, 52, 54, 62, 64 included in the inverter circuit 6 may be collectively referred to as a conversion switching element group.

Each of the above-mentioned switching elements is a transistor (power transistor) for power conversion. Each switching element is, for example, an IGBT (Insulated Gate Bipolar Transistor).

Next, the hardware configuration of the power converter 1 of the embodiment will be described with reference to FIGS. 2 and 3. FIG. 2 shows a side view of the power converter 1. The case 70 of the power converter 1 is divided into an upper cover 72, an upper case 74, and a lower case 76. The upper case 74 has upper and lower openings, the upper opening is closed by the upper cover 72, and the lower opening is closed by the lower case 76. The upper cover 72 is attached to the upper case 74 with a plurality of bolts 80. The lower case 76 is attached to the upper case 74 with a plurality of bolts 82. The lower case 76 is provided with a connector hole 79 to which a connector (not shown) of the power cable 18 (see FIG. 1) extending from the motor 8 is connected. Three connection bus bars 18a connected to the connector of the power cable 18 face the connector hole 79. The connector hole 79 is provided on the side surface of the lower case 76.

The internal structure of the power converter 1 will be described with reference to FIG. FIG. 3 is a cross-sectional view of the power converter 1 along lines III-III of FIG. A controller 10 is arranged above the power converter 1. The controller 10 is a circuit board. The controller 10 is fixed on the middle plate of the upper case 74. The filter capacitor 12 and the smoothing capacitor 14 of FIG. 1 are built in the capacitor module 24. As shown in FIG. 3, the capacitor module 24 is arranged on the negative side in the Y-axis direction (that is, the left side of the drawing) of the case 70 of the power converter 1. A plurality of semiconductor modules 30, 40, 50, 60 (see FIG. 1) included in the power converter 1 are built in the stacking unit 46. The stacking unit 46 is configured by laminating a plurality of semiconductor modules in which two switching elements are sealed with a resin and a cooler for cooling the semiconductor modules. On the lower side of the stacking unit 46, three terminals extending in the Z-axis direction are provided. The terminal located on the leftmost side is the positive electrode terminal 46a. The positive electrode terminal 46a is connected to the capacitor module 24 by a positive electrode bus bar 47. The terminal located at the center is the negative electrode terminal 46b. The negative electrode terminal 46b is connected to the capacitor module 24 by a negative electrode bus bar 48. The terminal located on the far right is the midpoint terminal 46c. As shown in FIG. 3, the midpoint terminal 46c is connected to the connection bus bar 18a via the output bus bar 49. As described above, the connection bus bar 18a is connected to the motor 8 shown in FIG. 1 via the power cable 18. That is, the output of the inverter circuit 6 is sent to the motor 8 via the connection bus bar 18a and the power cable 18. As shown in FIG. 1, the power cable 18 is composed of three cables. Therefore, the connection bus bar 18a connected to the power cable 18 is also composed of three bus bars as shown in FIG. Here, one bus bar of the connecting bus bars 18a will be described, but the same applies to the other two bus bars.

As shown in FIG. 3, the connection bus bar 18a penetrates the terminal block 17 and extends toward the connector hole 79. As described above, the connection bus bar 18a is connected to the power cable 18 via the connector hole 79. A current sensor 16 is provided inside the terminal block 17. The shape of the current sensor 16 when viewed from the positive side in the Y-axis direction is shown on the right side of FIG. The current sensor 16 includes a ring core 16a that surrounds the connection bus bar 18a, and a Hall element 16b that is arranged in the gap of the ring core 16a. The ring core 16a is made of a magnetic material. The ring core 16a collects the magnetic flux generated by the current flowing through the connecting bus bar 18a. The Hall element 16b measures the magnetic flux passing through the ring core 16a. The current sensor 16 can obtain the current value flowing through the connecting bus bar 18a from the magnetic flux passing through the ring core. The current sensor 16 is a Hall element system that obtains a measured value of the current by utilizing the Hall effect from the magnetic flux generated by the current of the connecting bus bar 18a. The current sensor 16 is connected to the controller 10. Based on the measured value measured by the current sensor 16, the controller 10 controls a plurality of switching elements included in the converter circuit 4 and the inverter circuit 6 shown in FIG. The current sensor 22 shown in FIG. 1 is also a Hall element type current sensor including a ring core and a Hall element, similarly to the current sensor 16.

Here, the Hall element 16b has a resistance value for measuring the magnetic flux passing through the ring core 16a. The strength of the magnetic flux output by the Hall element 16b changes depending on this resistance value. The resistance value of the Hall element 16b changes, for example, depending on the temperature characteristics. That is, the current sensor 16 provided with the Hall element 16b may have a deviation of the zero point (origin) due to the temperature characteristics. In order to correct the deviation of the origin of the Hall element 16b, the controller 10 corrects the origin based on the measured value of the current sensor 16. However, if the measured value of the current sensor 16 is incorrect, the controller 10 cannot accurately correct the deviation of the origin. When the error of the measured value of the current sensor 16 is large, the origin corrected based on the measured value of the current sensor 16 may be a more deviated origin from the origin before the correction.

Further, as shown in FIG. 3, a reactor 20 is arranged on the bottom surface of the power converter 1. Although details are omitted because it is well known, the reactor 20 is a coil in which a flat wire is wound edgewise, and a part of a ring-shaped core made of a magnetic material is inserted through the coil. The reactor 20 converts the current flowing through the coil into magnetic energy. Therefore, when a current flows through the coil of the reactor 20, a strong magnetic field is generated around the reactor 20. As shown in FIG. 3, the reactor 20 is arranged in the vicinity of the current sensor 16. As described above, the current sensor 16 measures the current that the Hall element 16b flows from the magnetic flux to the connection bus bar 18a. Therefore, the origin corrected based on the value measured by the current sensor 16 while the current is flowing through the reactor 20 may include a larger error due to the influence of the strong magnetic field generated from the reactor 20. ..

Hereinafter, the process executed by the controller 10 in order to more accurately correct the origin of the current sensor 16 (see FIG. 1) will be described with reference to FIG. The controller 10 first determines whether origin correction is necessary (step S2). Although not shown, the power converter 1 includes a temperature sensor, a voltage sensor, a rotation speed sensor of the motor 8 (see FIG. 1), and the like, in addition to the current sensor. For example, when the temperature changes drastically, as described above, there is a high possibility that the resistance value of the Hall element of the current sensor is affected. Therefore, the controller 10 determines that the origin correction is necessary when, for example, the temperature of the temperature sensor exceeds a predetermined value (step S2: YES). When it is determined that the origin correction is not necessary due to conditions such as temperature (step S2: NO), the controller 10 determines whether the origin correction has been executed for a predetermined time or longer (step S4). As a result, the controller 10 can execute the origin correction within a predetermined time even when the origin correction is not necessary due to conditions such as temperature. The predetermined time may be set by, for example, a temperature change measured by a temperature sensor.

When it is determined that the origin correction is necessary based on the conditions such as temperature (step S2: YES), or when the origin correction is not executed for a predetermined time or longer (step S4: YES), the controller 10 is shown in FIG. It is determined whether or not the indicated conversion switching element group is turned off (step S6). When the conversion switching element group is turned on (step S6: NO), there is a high possibility that a current is flowing through the current sensor 16 (see FIG. 1), so the controller 10 processes without origin correction. To finish. When the conversion switching element group is turned off (step S6: YES), the controller 10 determines whether the voltage switching element group is turned off (step S8).

When the voltage switching element group is turned off (step S8: YES), the origin is corrected based on the current value detected by the current sensor 16 shown in FIG. 1 (step S14). Specifically, the controller 10 replaces the measured value of the current sensor 16 when the conversion switching element group and the voltage switching element group are off with the zero point (origin) of the current sensor 16. When the conversion switching element group and the voltage switching element group are turned off, no current is flowing through the current sensor 16. That is, in this case, it is guaranteed that no current is flowing through the current sensor 16. Further, when the conversion switching element group and the voltage switching element group are turned off, no current is flowing through the reactor 20. Therefore, the current sensor 16 is not affected by the magnetic field generated from the reactor 20. In this way, by correcting the origin based on the measured value of the current sensor 16 when the conversion switching element group and the voltage switching element group are turned off, the controller 10 accurately determines the current sensor 16. The origin can be corrected.

Further, when the voltage switching element group is turned on (step S8: NO), the controller 10 determines whether the voltage switching element group can be turned off (step S10). Although not shown, the controller 10 determines that the voltage switching element group can be turned off, for example, when the rotation speed of the motor 8 is equal to or less than a predetermined value. When the power converter 1 is power running, the controller 10 turns off the voltage switching element group when it can be determined that the voltage switching element group does not need to boost the voltage (step S12). One example is the case where the position of the shift lever of the electric vehicle 100 is neutral and the vehicle speed obtained from the rotation speed of the motor 8 is low. Further, when the power converter 1 is regenerating, the regenerating current is equal to or less than a predetermined value, and it can be determined that the countercurrent voltage does not affect the conversion switching element group even if the voltage switching element group is turned off. In addition, the controller 10 turns off the voltage switching element group (step S12). As described above, the controller 10 included in the power converter 1 of the embodiment can increase the number of times the origin correction is executed by turning off the voltage switching element group under a predetermined condition. As a result, the accuracy of the current sensor 16 is improved.

The points to be noted in the examples are described below. As described above, the plurality of switching elements included in the power converter 1 of the embodiment are IGBTs (Insulated Gate Bipolar Transistors), but other transistors, for example, MOSFETs (Metal Oxide Semiconductor Field Effect Transistors). You may. Further, the converter circuit 4 included in the power converter 1 of the embodiment includes two voltage switching elements 32 and 34, but the switching element (upper switching element) 32 on the high potential side in FIG. 1 is indispensable. Not a component. In that case, the converter circuit becomes a DC-DC converter. Further, although the power converter 1 of the embodiment is mounted on the electric vehicle 100, it may be mounted on a hybrid vehicle including an engine. In that case, another inverter circuit for operating the engine may be provided.

Further, the controller 10 included in the power converter 1 of the embodiment measures the measured value of the current sensor 16 when the conversion switching element group and the voltage switching element group are turned off in order to correct the origin. It is replaced with the zero point (origin) of the current sensor 16. However, the techniques disclosed herein are not limited to this. For example, the controller 10 specifies an offset value from the difference between the measured value of the current sensor 16 when the conversion switching element group and the voltage switching element group are off and the origin (that is, zero). May be good. In that case, the controller 10 can correct the origin by adding the offset value to the measured value of the current sensor 16 after the offset value is specified.

Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of claims. The techniques described in the claims include various modifications and modifications of the specific examples illustrated above. The technical elements described herein or in the drawings exhibit their technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the techniques illustrated in the present specification or drawings can achieve a plurality of purposes at the same time, and achieving one of the purposes itself has technical usefulness.

1: Power converter 2: Battery 4: Converter circuit 6: Inverter circuit 8: Motor 10: Controller 12: Filter capacitor 14: Smoothing capacitor 16, 22: Current sensor 16a: Ring core 16b: Hall element 17: Terminal block 18: Power cable 18a: Connection bus 20: Reactor 24: Capacitor module 30, 40, 50, 60: Semiconductor module 32, 34: Voltage switching element 42, 44, 52, 54, 62, 64: Conversion switching element 46: Stacking unit 46a : Positive terminal 46b: Negative terminal 46c: Midpoint terminal 47: Positive positive bus 48: Negative negative bus 49: Output bus 70: Case 72: Upper cover 74: Upper case 76: Lower case 79: Connector hole 80, 82: Bolt 100: Electricity Car

Claims (2)

A booster circuit with a first switching element that boosts the voltage of the power supply,
A power conversion circuit having a second switching element that converts the output of the booster circuit into the drive power of the traveling motor, and
A current sensor that measures the current flowing between the power supply and the traveling motor, and
A controller that controls the first switching element and the second switching element based on the measured values of the current sensor, and
Is equipped with
The controller is a power converter that turns off both the first switching element and the second switching element and corrects the zero point of the current sensor based on the measured value of the current sensor at that time. The booster circuit includes a reactor connected between an input terminal connected to the power supply and the first switching element.
The current sensor is a Hall element system that obtains a measured value of current by utilizing the Hall effect from the magnetic flux generated due to the current to be measured.
The power converter according to claim 1.

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